Alloys of rhodium and nickel



Patented Jan. 5, 1937 I ALLOYS OF RHODIUM AND NICKEL Edmund M. Wise,Westfield, and Raymond F.

Vines, Elizabeth, N. J., assignors to The International Nickel Company,Inc., New York, N. Y., a corporation of Delaware No Drawing. ApplicationDecember 5, 1934, Serial No. 756,046

3 Claims. (01. 75-170) The present invention relates to alloys ofrhoinvention to reduce the cost of high grade foundium and nickel, andmore particularly to a tartain pens by producing an alloy containingrhonish and corrosion resisting alloy containing rhodium and nickelsuitable for the production of dium and nickel, which is suitable forpen nibs pen nibs at a substantial saving in cost.

5 and other uses where high stability and moderate Theinvention furthercontemplates the provi- 5 cost are essential. sion of anoble white alloyof rhodium and nickel It is known that the writing fluids used infounsuitable for pen nibs and other uses where high tain pens have astrong corrosive action on thestability and moderate cost are essential,which pen nib and that heretofore high grade pen'nibs contains no gold,thereby offering an effective have been made almost entirely from caratgold means for conserving gold and releasing it for 10 alloys,particularly 14 k. gold, which withstood essential monetary purposes.satisfactorily the corrosive action of the writing It is also an objectof the invention to provide a fluids. The use of gold pen nibs,.however,was White noble alloy containing rhodium and nickel expensive andincreased the cost of fountain pens suitable for pen nibs and similarpurposes, which l5 considerably, especially in view of the recent can bemade on an industrial scale, which can be 15 increase in the price ofgold. The art has been handled, fabricated and worked withconvenconstantly endeavoring to reduce the cost of tional appliances andequipment, and which is fountain pens and to produce pen nibs which-wererelatively cheap and permits wide commercial less expensive and could bemanufactured more and industrial use.

economically than gold pen nibs and which Other objects and advantagesof the invention 20 possessed the requisite tarnish and corrosion rewillbecome apparent from the following descripsistance, durability and otherqualities of the gold tion. nibs. Although many attempts have been madeGenerally speaking, the present invention conto provide the trade andthe public with an alloy templates providing an alloy containing rhodiumsuitable for pen nibs having the required resistand nickel, in which therhodium content may 5 ance to tarnish and corrosion, workability, varyfrom about 25% to about 80%; We have strength, moderate cost, etc., noneas far as we found that the rhodium-nickel alloys containing are awarehas been wholly satisfactory and sucfrom about 25% to about 80% ofrhodium have cessful in practical, commercial and industrial excellentphysical properties, are easy to cast and use. to work, and areresistant to tarnish and to cor- 30 We have discovered that alloys ofrhodium and rosion, particularly to ink corrosion. Special nickel ofcertain composition are less expensive. characteristics of the alloysare a high modulus than gold alloys and possess such excellent resistofelasticity and a low density, as compared to ance to tarnish and tocorrosion, especially to ink known gold alloys. Pen nibs can bemanufaccorrosion, combined with suitable hardness, elastured from therhodium-nickel alloys of the pres- 35 ticity, workability, etc., as tobe fully adapted for ent invention at a substantially less cost than usein the production of high grade pen nibs and gold pen nibs, can besoldered or welded to osmifor other uses where high stability andmoderate Y ridium tips easily and economically, and in actual cost areessential. use are entirely satisfactory and resist tarnish 40 It is anobject of the present invention to pro and the corrosive action ofwriting fluids indefi- 40 vide an alloy containing rhodium and nickel,nitely. Furthermore, their excellent physical which is strong, hard,readily workable, and properties and especially their high modulus ofwhich can be easily soldered or welded to osmielasticity permits use ofthinner'sections than is ridium alloys. possible with carat gold alloys,while their lower It is another object of the invention to providedensities aid in lowering considerably the cost 45 an alloy containingrhodium and nickel, which per nib over that of carat gold.

possesses high resistance to tarnish and to corro- In general thetarnish and corrosion resistance sion, and which is not attacked byordinary writof the rhodium-nickel alloys imp Wlth ing fluids. creasesin the rhodium content of the alloy. We

A further object of the invention'is to provide have foundthat thosealloys containing about 50 a white noble alloy containing rhodium and 35of rhodium with nickel constituting subnickel, which is relativelyinexpensive and which stantially the balance resist successfully thecorcan be cast and fabricated easily and economi-' rosive action of inkand are especially suitable for I cally. high grade pen nibs.

It is within the contemplation of the present The alloys containing 35%or more of rhodium 56 are so noble that they are completely resistant tocorrosion by strongly corrosive solutions such as 25% aqueous ferricchloride solutions or concentrated nitric acid. When the rhodium contentof the alloys exceeds 60%, the alloys become resistant even to aquaregia. Of course, these alloys are not attacked by the ordinary writingfluids used in fountain pens.

We have discovered that the addition of palladium to the rhodium-nickelalloys improves the properties and especially the corrosion resistancethereof. Thus, we found that palladium may be added to further improvethe homogeneity of the alloy when desired. Where the rhodium content ofthe alloy is slightly too low to give complete passivity to very activecorrosives and a small amount of pitting would result, we found that theintroduction of a small amount of palladium to the binary rhodium-nickelalloy will further ennoble the alloy and prevent pitting. With theaddition of larger quantities of palladium and when a considerablepercentage of the nickel is replaced by thepalladium, the alloys arestill further ennobled and are adapted for those uses where resistanceto highly corrosive media is derived. We found that as high as 55% ofpalladium may be added advantageously to rhodium nickel alloys. Thecomposition of most useful rhodium-nickel alloys containing palladiummay vary from about 25% to about (expressed in weight percent) ofrhodium, from about 20% to about 75% nickel and may contain up to about55% palladium. The hardness of the alloys con taining palladium varieswith the combined rho dium plus palladium content of the alloy fromabout 80 to about Rockwell B hardness. An alloy containing about 40%rhodium, 20% palladium and 40% nickel is suitable for uses where severecorrosion conditions are encountered.

Part of the rhodium may be replaced atom for atom by platinum oriridium, although this increases the cost of the alloy over that of thebinary rhodium-nickel alloy. Molybdenum or tungsten may be added toharden the alloy. When adding molybdenum or tungsten, we have discoveredthat the resistance of the alloy to corrosion by chlorides is alsoincreased. A part of the nickel may be replaced by cobalt, iron, orcopper, but such additions usually result in some degradation of thecasting, physical or corrosion properties of the alloy and are notgenerally advantageous.

By controlling the composition or the proportion of the ingredient ofthe alloy of the present invention, as hereinabove more fully described,the alloy may be made to possess a wide range of physical and chemicalproperties and be adapted for a large number of uses and applications.Thus, the alloy may be employed for uses other than pen nibs where highstability, corrosion and erosion resistance and an excellent white colorcoupled with moderate cost are essential. In connection with theapplication of the new alloy to chemical work its peculiar resistance tochlorides is notable and particularly valuable for it will remainsubstantially unattacked where numerous other corrosion resistingalloys, particularly those relying upon chromium for passivity, arewholly destroyed. The resistance to nitric acid becomes complete at 25%rhodium or below and remains high throughout the range of compositionscontemplated by the present invention. The high melting point andnobility of the new alloy render it particularly useful for dental usessuch as tooth pins, lingual bars and for electrical uses such aselectrodes in electrochemical apparatus and the like. The brilliantwhiteness of the high rhodium content alloys particularly thosecontaining 65% to about 80% rhodium and their resistance to corrosiveinfluences and freedom from tarnishing on outdoor exposure suggest theiruse for reflectors in searchlights and optical instruments and the like.

In preparing the rhodium-nickel alloys of the present invention, we havefound that certain impurities and especially sulphur or sulphurlikeimpurities are harmful and render the alloy unworkable and difficult tocast. We discovered that if the rhodium-nickel alloys of the compositiondescribed are properly melted and are kept free from oxygen, sulphur,tellurlum, selenium and similar elements, the alloys possess a highdegree of ductility and can be cast and rolled without difiiculty. Thus,we found that the addition of sufficient amounts of suitable deoxidizingand desulphurizing elements such as magnesium, zinc, manganese, silicon,boron, barium, calcium, titanium, zirconium and the like improves thecasting and working properties of the alloys. A low carbon content ofthe alloy is also desirable in achieving maximum ductility.

In manufacturing the rhodium-nickel alloys of the present invention, weprefer to melt the pure component metals preferably in a high frequencyfurnace. In this melting it is desirable to employ a carbon freecrucible lined with a suitable magnesia refractory or, if preferred,with lime. When the melt has been completed, the alloy is allowed tosolidify in the crucible. The solid alloy is then remelted and asufficient amount of a suitable desulphurizing and/or deoxidizing agentis added, for instance 0.1% of magnesium may be added as anickel-magnesium alloy, and is then cast into a suitable graphite mold.The alloy may then be hammered and annealed at 900 C.- 1000 C. inhydrogen and rolled in the usual manner.

The term desulphurizing element is herein used to mean an element whichwill fix not only sulphur but also the sulphur group elements comprisingselenium and tellurium.

We have found that some lots of commercial rhodium yield brittle alloyspresumably due to the presence of a trace of sulphur group elements suchas tellurium. We have found that if such rhodium is purified prior toalloying with the nickel, it produces ductile alloys. Thus the rhodiummay be purified chemically. We have also discovered that the rhodium maybe purified by melting it prior to the addition of nickel and bysubjecting it to alternate oxidation and reduction over a period ofabout 30 minutes. The rhodium is then allowed to solidify, the nickel isadded and the whole is then melted, treated with a suitable deoxidizer,such as magnesium or the like, and cast. The subsequent treatment may beas in the first example. We have found that the alloys of rhodium andnickel of the present invention prepared according to the precautionsgiven hereinabove possess a high degree of ductility; are easily cast,and can be worked and fabricated into various forms and shapes easilyand economically. Furthermore, the alloys are strong, sufliciently hard,have a high modulus of elasticity, can be welded readily, for instanceto osmiridium alloys, and possess high resistance to tarnish and tocorrosion.

The following table sets'forth by way of example the composition, thecomparative cost per unit weight and per unit volume, and the hardnessof some useful alloys of the present invention and of a known 14 kt.white gold alloy.

Weight Rh 37 Cost/oz. $16.65 Ni 63 Cost/cc. 5.32

Rockwell B hardness, annealed-80 Rh 35.9 Cost/oz. $16.25 Mo -6.7Cost/cc. 5.18

Rockwell B hardness, annealed92 Rh 28.4 Cost/oz. $16.20 Pd .14.?Cost/cc. 5.28

Rockwell B hardness, annealed-88 Rh 64 v I Cost/oz. $28.90 Ni; .36Cost/cc. 10.10

Rockwell B hardness-92 I 14 is. white gold Au 58.33 Cost/oz. 20.40 (In-.1'7.97 Cost/cc. 8.36 Ni .17 .70

Rockwell B hardness, annealed-94 It is to be observed that the presentinvention provides. a new noble white alloy containing rhodium andnickel, which is relatively inexpensive, easy to cast and work, whichhas sufiicient hardness, strength and good wearing qualities, which hasa high modulus of elasticity and low density, and which is resistant totarnish, to corrosion, and especially to corrosion by writing fluids.

It is further to be noted that the rhodiumnickel alloys of the presentinvention are especially suitable for pen nibs, that high grade pennibs. can be manufactured from the alloys at a substantially less costthan gold pen nibs, can

be soldered or welded to osmiridium tips easily and economically, and inactual use are entirely satisfactory and resist tarnish and thecorrosive action of writing fluids indefinitely.

Furthermore, it is to be observed that the alloy of the presentinvention has a brilliant white color, that by properly controlling thecomposition thereof, as hereinabove more fully described, may be made toresist corrosion by chlorides, concentrated nitric acid and even aquaregia, and accordingly may be employed for uses other than pen nibs,where high stability, corrosion and erosion resistance, and an excellentwhite color coupled with moderate cost are essential.

Moreover, it is to be noted that the invention provides a relativelyinexpensive noble white alloy suitable for pen nibs and other purposeswhere high stability and moderate cost are essential, which contains nogold, thereby ofiering an efiective means for conserving gold andreleasing it for essential monetary purposes.

Although the present invention has been described in conjunction withpreferred embodiments, it is understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention,'as those skilled in the art will readilyunderstand.

We claim: 1. A corrosion resistant alloy composed of about 25 to ofrhodium and the balance consisting of substantially all nickel, saidalloy being corrosion resistant to writing fluids.

2. A corrosion resistant alloy composed of about 35% rhodium and thebalance consisting of nickel, said alloy being corrosion resistant towriting fluids.-

3. A corrosion resistant alloy composed of about 65% rhodium and thebalance consisting of nickel, said alloy being corrosion resistant towriting fluids.

EDMUND M. WISE. RAYMOND F. VINES.

